Various types of golf bag coolers are known in the prior art. However, what is needed is a triangular golf bag cooler that includes a triangular longitudinal cross-section configured to fit the triangular golf bag cooler within an extant golf bag pocket, the triangular golf bag cooler having a gel layer disposed between an outer liner and an interior liner; said gel layer freezable with a high specific heat capacity to provide extended cooling to items stored within an interior cavity; a drain plug disposed in a first side to drain condensation and melt water from the interior cavity, the triangular golf bag cooler collapsible when empty for easy portage and storage, to provide ready access to food items proximal to the golfer's clubs when playing on a fairway.